The present invention relates to a pressure monitoring device and more particularly to a pressure monitoring device which is adapted to couple a source of fluid with a tripping device in such a manner that a tripping signal is generated when the pressure of the fluid being monitored passes a certain predetermined limit.
It is often desirable to couple pressure monitoring devices to fluid systems employing pressurized fluids in order to monitor the fluid pressure and generate a signal if the pressure passes predetermined limits, i.e., goes above a high pressure limit or below a low pressure limit. The signal generated when the pressure passes the predetermined limit may for example be an alarm signal to actuate an alarming device such as a light or buzzer, or the signal may be used to actuate a device to adjust the pressure of the fluid or even shut down the system. In such systems employing pressure monitoring devices, it may also be desirable to prevent generation of the tripping signal when the monitoring device is by-passed and/or disconnected from the fluid system, in order not to generate a "false" tripping signal.
For example, pressure monitoring devices are useful in dialysis systems to monitor the pressure of the blood being dialized and to generate a tripping signal in the event that the blood pressure falls below a certain limit. Further, it may be desirable in such systems that the tripping signal not be generated when the blood lines are disconnected from the dialysis system and/or patient.